<!DOCTYPE html>
<!-- Nothing on this page should be scrollable. -->
<style>
  body {
    margin: 0;
  }

  .red {
    background: red;
    position: absolute;
    width: 100%;
    height: 100%;
    overflow: hidden;
  }

  .green {
    background: green;
    position: absolute;
    width: 500px;
    height: 100%;
    right: 0px;

    width: 500px;
    transform: translateX(250px);
    box-shadow: 0px 0px 200px black;
  }
</style>

<div class="red">
  <div class="green"></div>
</div>

